Placing tool with means for contolling placing processes

ABSTRACT

In order to provide improved monitoring of riveted connections during rivet setting, a rivet setting tool comprising a head piece for holding a rivet, a device for gripping a rivet pin and a pulling apparatus connected to the device for gripping a rivet pin is provided, which additionally comprises a device for measuring the tension of the pulling apparatus. Using the setting implement according to the invention, a cause of a fault can be determined by means of a comparison between measured values and stored values.

The invention relates to a setting tool having means for monitoringsetting operations.

Setting tools having means for monitoring the setting operation areknown.

For example, in DE 44 01 134, a method is described in which a forcecomponent is measured over the distance of the stroke and compared witha desired curve. The intention is to monitor whether the settingoperation has been carried out properly.

EP 0 738 551 (U.S. Pat. No. 5,666,710) discloses an apparatus forchecking the setting of blind rivets. Here, the tensile force and theposition of the draw shaft are measured. The energy converted isdetermined via an integrator and compared with a desired value.

The disadvantage with these known means for monitoring the settingoperation is that, although it is possible to determine with a certainprobability whether the setting operation lies within a given tolerancelimit, the cause of a fault cannot be determined. During a settingoperation, a whole series of faults can arise. For example, errors madeby the operator, for example as a result of skewed placement of thesetting implement, excessively wide holes, wrong rivets, faults in therivet itself. In the case of blind rivets, there is also always the riskthat the rivet will grip only the part to be fixed but not thecounterpart.

It is an object of the invention to provide a setting implement whichmonitors the setting operation and, in the process, also detects thecause of a fault that occurs. Furthermore, it is an object of theinvention to permit comprehensive monitoring of various parameters of asetting operation.

This object is already achieved in a surprisingly simple way by asetting tool according to the features of claim 1. According to saidclaim, a setting tool comprising a head piece, in particular for holdingthe rivet, a device for gripping and/or pulling and a pulling apparatusconnected to the device for gripping and/or pulling is provided, whichhas means for measuring the variable values occurring during the settingoperation, a device for comparing the measured values with stored valuesand also a device for determining a cause, in particular a cause of afault, for the deviation of measured from stored values.

The setting tool, which can be of an extremely wide range of types, forexample rivet setting tools, blind rivet nut setting tools, locking ringbolt setting tools, has sensors. By means of the sensors, variousparameters such as the position of the pulling apparatus, the time sincethe start of the setting operation or the tension exerted can bemeasured. These measured values are compared with stored values. Thestored values contain not only a desired curve, a faulty settingoperation being assumed if it is not complied with, but also values forspecific faults. These values can be available as a simple individualvalue or else as a desired curve with various parameters which describea specific fault. The set of stored causes of faults comprises at leastone cause of a fault, which may already be sufficient in someapplications. Preferably, however, a plurality of different causes offaults is stored. In addition to faults, the cause of deviations which,although they lie within the tolerance band, are not ideal, can also bedetermined. In this case, the setting implement is preprogrammed for aquite specific setting operation which, for example, is defined by therivet used, the material used and its thickness. Programming for aplurality of different setting operations is also conceivable. Theinvention makes it possible to correct the cause of the fault as quicklyas possible. Since operating errors are also registered with theinvention, the setting implement is also very well suited to untrainedoperators. By means of the invention, the quality of each settingoperation can be monitored. This is of great advantage, for example, inaircraft engineering. There, although use is made to some extent ofrivets which have been subjected to x-ray inspection, it is not possibleto ensure by means of the inspection whether the riveting operation hasthen proceeded without fault. Using the invention, it would in theoryeven be possible to dispense with the complicated x-ray inspection andnevertheless to be able to guarantee the durability of the rivetedconnection.

Preferred embodiments and developments of the invention can be gatheredfrom the respective subclaims.

In a preferred embodiment of the invention, the measured variable valuescomprise the tension exerted by the pulling apparatus and/or theposition of the pulling apparatus and/or the time since the start of therespective setting operation and/or the angle with respect to thesurface on which the setting implement is placed. By means of thesevalues, comprehensive fault diagnosis is possible. This can also becarried out by converting the values into curves or multidimensionalcharacteristic maps.

In a preferred embodiment of the invention, monitoring is carried out asto whether the implement has been placed at the correct angle. Theoperators frequently do not place the setting implement accurately atthe correct angle. As a result, there is a reduction in the strength ofthe connection.

It is expedient also to monitor whether a wrong rivet has been used. Forexample, there are also rivets which do not differ visually but consistof different material and therefore have a completely differentstrength. This can be determined, for example, by means of the curve ofthe tension exerted by the pulling apparatus.

With a further embodiment, monitoring is carried out as to whether therivet is damaged. For example, material faults in the rivet lead to adifferent force curve.

A further embodiment monitors whether the hole provided for the rivet istoo wide or too narrow.

Also, whether there is a rivet in the implement can easily be determinedby the setting tool according to the invention, for example by measuringthe tension exerted.

It is particularly expedient to monitor whether the rivet is grippingboth parts to be connected. Particularly in the case of blind rivets, itfrequently occurs that the rivet does not grip both parts to beconnected. The operator cannot monitor this himself either, since hesees only the part to be fixed but not the other side. If the rivetgrips only the part to be set, the tension exerted by the pullingapparatus rises later, for example at a greater stroke. The fault caneasily be determined in this way.

In a further embodiment of the invention, monitoring is carried out asto whether the setting tool has a defect. For example, the oil level ofthe pulling apparatus can be too low. Consequently, the pullingapparatus becomes stiff and no longer operates with the envisagedtensile force.

Ideally, a plurality of these causes of faults is programmed into animplement. The programming of the implement can be carried out byperforming a series of tests, in which faults are made deliberately. Thedeviations of the measured values occurring in the case of therespective faults can then be stored in the implement, in order to becompared with values measured later. It is also conceivable not only toperform pure fault monitoring but also to compare the deviation of asetting operation still lying in the respective tolerance area with anideal value.

A preferred embodiment of the invention has a device for measuring theposition of the pulling apparatus and/or for measuring the tensionexerted by the pulling apparatus. The position of the pulling apparatusand the tension exerted are two of the most important parameters viawhich a whole series of causes of faults can be determined.

As provided in an expedient embodiment of the invention, the tensionexerted by the pulling apparatus is measured with a strain gage. Such astrain gage for measuring stresses is reliable and inexpensive. Thetension is substantially proportional to the tensile force exerted bythe pulling apparatus.

In an alternative embodiment, the device for measuring the tensionexerted by the pulling apparatus comprises a piezoelectric sensor. Thispiezoelectric sensor needs no voltage supply.

In order to measure the position of the pulling apparatus, an expedientembodiment of the invention comprises a capacitive sensor. Such acapacitive sensor is substantially more accurate as compared withoptical sensors frequently used.

In one development of the invention, the angle with respect to thesurface on which the setting implement is placed is measured by means ofat least three sensors arranged on the implement head. These sensorscontact the surface on which the implement is placed if it is placed atthe correct angle. In this way, a frequent error made by the operatorcan be diagnosed.

In one development of the invention, the setting tool has means for datastorage and/or further processing. For example, the measured values canbe evaluated statistically. The user can, for example, monitoraccurately how many setting operations have been made, how many of thesewere faulty and what causes there were for faults. Furthermore, it isconceivable to evaluate the values of the setting operations which haveproceeded correctly, for example in the form in which deviations of thevalues from the ideal values are stored and evaluated. In this way,comprehensive quality control is possible.

The manufacturer of the tool can monitor the function of his implement.It is also conceivable that the tool is not paid for per se but that themanufacturer makes the tool available to the customer and the latterthen pays, for example, according to the number of setting operationscarried out. In addition, to grant a manufacturer guarantee, it isextremely advantageous if the manufacturer can detect potential faultsthrough the tool itself and, if appropriate, exclude them.

In an expedient embodiment of the invention, the means for data storageand further processing can be reset, in particular during an implementservice. In this way, for example, the implement can be issued to thecustomer like a new implement after being reset.

An expedient embodiment of the invention has a chip for the comparisonof measured and stored values and/or for the data storage and furtherprocessing. Such a chip can be tailored exactly to the requirements ofthe implement. Furthermore, the smallest possible overall size is thuspossible. As compared with EPROMs, which can also be used, the chipadditionally offers the advantage that it is substantially moredifficult to manipulate.

In an expedient embodiment of the invention, the comparison of measuredand stored values and/or the data storage and further processing arecarried out in the implement. By means of modern microelectronics it ispossible to integrate the entire evaluation into a handheld implement.

An independent power source, in particular a rechargeable battery, isexpediently provided in the implement for the means for comparingmeasured and stored values and/or for the data storage and furtherprocessing. In this way it is ensured that stored measured values arenot lost, even in the event of a relatively long power failure.

The setting implement expediently has a counter which counts rivetsetting cycles and/or faults and/or causes of faults. In this way,statistical fault evaluation is even possible with the implement itself.

In a development of the invention, the setting implement has a devicefor registering the date and/or time of day. In this way, the settingoperations and possible faults can be assigned to a specific time. It isthus possible subsequently to understand when and as a result often alsowhere exactly a specific fault has occurred.

A development of the invention has a device for transmitting measuredvalues to an external unit. Conceivable as an external unit is, forexample, a computer system, by which further storage and evaluation ofthe measured values supplied by the setting implement can be performed.The individual setting implements could, for example, be assigned to thesystem via their implement numbers.

The device for transmitting measured values expediently has a device fortransmitting infrared, ultrasound or radio signals, in particular“Bluetooth”. Thus, for example with Bluetooth technology, there is aninexpensive and reliable standard component for wire-free transmission.

As an alternative to this, the external unit can comprise a mobile radioterminal. Thus, wire-free transmission is possible even over longdistances, for example to the manufacturer of the setting implement.

In an expedient embodiment of the invention, the setting tool has adevice for switching off the rivet setting implement and/or indicatingthe cause of a fault in response to a signal generated in the event of afaulty rivet setting operation. Thus, for example, it is also possiblenot to carry out a setting operation at all if a fault is indicated fromthe start. If the device is not placed at the correct angle, it does nottrigger at all; likewise, if there is no rivet in the implement. Evenif, when setting a blind rivet, only the component to be fixed isgripped, aborting the setting operation is still possible, whileindicating the cause of a fault.

It is also conceivable to generate the signal by means of an externalunit, for example a connected computer.

In a development of the invention, the setting tool can also contain adevice for connection to a local network, which means that fastertransmission and further processing of the data are possible. Within thecontext of mounting steps following one another, for example on theproduction line assembly, rapid reporting of a fault is particularlyadvantageous, in order that the entire mounting process does not falterfor a long time.

The pulling apparatus of the setting implement can be operatedelectrically, in particular with a rechargeable battery,electrohydraulically, hydraulically or hydropneumatically. It is alsopossible to provide a fully cordless implement with a rechargeablebattery and wire-free data transmission.

In a development of the invention of a non-cordless implement, thesetting implement has a line for the supply of compressed air or powerand at least one further line for the transmission of the measuredvalues, and the further line, together with the one line, forms onestrand with one connection. Thus, it is not necessary for two lines tobe connected for power supply and data interchange. It is conceivable toprovide a combined connector with, for example, a compressed air lineand adjacent lines for the data transmission.

In one development of the invention, the setting tool carries out a testcycle after being switched on. In this way, faults which relate to theimplement can be ruled out even before use. For instance, in order tomonitor whether the tool is in order mechanically, the pulling apparatuscan be moved forward and back automatically after being switched on. Inthe event of stiffness of the pulling apparatus, the tool indicates thefault.

The object of the invention is also achieved by a method for monitoringsetting operations, in particular rivet setting operations, according tothe features of claim 28.

According to said claim, a part to be set is inserted into a settingimplement, preferably a setting implement as described above, and then atensile force is exerted on the part to be set by means of a pullingapparatus.

The values which occur during the setting operation are measured. Thevalues measured in this way are compared with stored values. Finally, byusing this comparison, the cause of a deviation of measured from storedvalues is determined from a set of stored causes.

Furthermore, the invention according to the features of claim 38 relatesto a head piece for a setting tool, comprising means for measuring thevariable values occurring during the setting operation, comprising adevice for comparing the measured values with stored values and alsocomprising a device for determining the cause of the deviation of themeasured from the stored value from a set of stored causes. This headpiece fulfills the task according to the invention just like the settingimplement. A head piece makes it possible to equip an existing settingimplement with the functions according to the invention.

Furthermore, the invention relates to a setting tool comprising apiezoelectric sensor and a method for setting parts to be set,preferably rivets, in particular an apparatus and a method for settingrivets with tension measurement, and also a head piece for a settingtool.

Riveted connections are used in industrial fabrication in many ways forjoining components. In particular in the automobile and aircraftindustry, under the aspect of safety, high requirements are placed onthe stability and long-term loadbearing ability of subassemblies. Thestability of a riveted connection depends to a critical extent on theprogress of the riveting operation. For example, if the early pin of ablind rivet shears off too easily, the strength and durability of theriveted connection is endangered or at least not optimal. This issimilarly true, for example, if the blind rivets have not been insertedstraight into the opening in the metal sheets, or the opening for therivet is not matched optimally. The latter occurs, for example, as aresult of non-round openings or those with wrong diameters.

Known riveting tools set rivets with preset parameters, such as thetensile force to be applied. Under optimum conditions, a rivet settingoperation using such an implement may likewise lead to an optimumresult, but deviations from the desired parameters, which influence thestrength of the connection, are not recognized in this case. This isimportant in particular, since a defective riveted connection underexternal checking can quite possibly give the impression of a correctlyset blind rivet or a riveted nut. Such faulty connections havedetrimental effects on the quality of the subassemblies producedtherewith and, in regions that are sensitive with respect to safety,such as aircraft construction, can even have fatal consequences.

EP 0 454 890 discloses a rivet setting implement which is provided witha force measuring device which ensures that the rivet setting implementoperates with a predefined tensile force. The force measuring device hasa strain gage. The disadvantage with such a strain gage is that a powersupply is needed for this and that the strain gage does notintrinsically convert the tensile force into a voltage signal.

The present invention has therefore taken the object of providingimproved monitoring of riveted connections during rivet setting. Thisobject is already achieved in an extremely surprisingly simple manner bya setting tool as claimed in claim 60, and by a method for setting asclaimed in claim 77 and by a head piece for a setting tool as claimed inclaim 82. Advantageous developments are specified in the respectivedependent claims.

Accordingly, a rivet processing tool, in particular a rivet settingtool, having a head piece for holding a rivet, in particular, a devicefor gripping and/or pulling a rivet pin, in particular, and a pullingapparatus connected to the device for gripping and/or pulling a rivetpin, in particular, is provided which, in addition, has a devicecomprising at least one piezoelectric sensor for measuring the tensionof the pulling apparatus.

By means of the device for measuring the tension of the pullingapparatus, the measured values of the latter can be determined andevaluated. It has been shown that a measurement of the tension variationduring a rivet setting cycle reproduces detailed information about therivet setting operation and, in particular, faulty rivet settingoperations can be determined by using the tension variation.

The piezoelectric sensor used for the measurement of the is tension isinexpensive, supplies exact measured values and can be accommodated inan extremely small space.

Furthermore, such a sensor supplies a voltage signal. Thus, as distinctfrom the strain gages conventionally used, a power supply is notrequired.

The invention is suitable for all types of rivet processing and settingtools, for example including rivet setting tools, blind rivet nutsetting tools, locking ring bolt setting tools, etc.

For the monitoring of the setting operation, additional parameters canbe recorded. For example, the instantaneous position of the pullingapparatus can advantageously be determined by a device for determiningthe position of the pulling apparatus, such as a displacementtransducer, so that it is possible to evaluate tension-displacementvalue pairs.

The tension can be measured indirectly in a straightforward manner bymeans of a pressure sensor which, for example, measures the opposingforce exerted by the pulling apparatus on a part of the rivet settingtool.

In particular for industrial applications, hydraulically operatedpulling apparatuses are advantageous, with which fast setting cycleswith reproducible setting parameters can be carried out. However, theinvention also comprises electrical, electrohydraulic and hydropneumaticpulling apparatuses. Among the electrical pulling apparatuses, acordless implement with integrated rechargeable battery is particularlyadvantageous.

For registering and evaluating the tension measured values from thedevice for measuring the tension of the pulling apparatus, anappropriate device can advantageously be accommodated in the settingimplement. Furthermore, a counter which counts setting cycles can beaccommodated in the setting implement. By using a counter which recordsthe number of setting cycles carried out by using the tension measuredvalues, maintenance intervals can be monitored, for example. Inaddition, the counter can be used for the purpose of monitoring whetherany rivets have possibly been left out, in particular in the case oflarge subassemblies with a large number of rivets.

The device for evaluating and registering can also comprise a dateand/or time registering device. For example, by means of dateregistration, guarantee periods and maintenance periods can be checked.The implement can be set up, for example, in such a way that it startsthe date registration after a certain number of rivet setting cycles, sothat sample cycles can be carried out before the start of the dateregistration, for example. With additional registration of the time ofday, it is possible, for example, to trace back the time at which faultyrivets were set.

The tension measured values and/or the counter readings can also betransmitted to an external unit by an appropriate device for thetransmission of tension measured values. This unit can be, for example,a computer for the data evaluation and/or control. The signaltransmission can advantageously in this case be accomplished by a devicefor transmitting infrared, ultrasound or radio signals.

Furthermore, the data can also be transmitted via a mobile radio networkto a mobile radio terminal. By means of this the data can be transmitteddirectly to a maintenance department or to the manufacturer, for examplefor remote diagnoses in the event of faulty functioning of theimplement. Likewise, the manufacturer can consequently check whether therequired maintenance intervals have been complied with.

The device for gripping a rivet pin preferably additionally comprisesclamping jaws which are actuated via a chuck connected to a drawspindle. The tension is in this case transmitted via a draw spindle.

The setting implement can also be provided with a device for connectionto a local network for faster distribution of the data to a plurality ofexternal evaluation units.

It is also within the scope of the invention to specify an appropriatemethod of monitoring setting operations which, in particular, can becarried out with a setting implement according to the invention. Themethod provides for a part to be set to be inserted into an openingprovided for the purpose and then, in order to set the part to be set,for a tensile force to be exerted on the part to be set, preferably therivet pin, by means of a pulling apparatus, during the application ofthe tensile force at least one measured value being obtained which iscaused or influenced by the tensile force applied to the rivet pin. Themeasured value can in this case be obtained at a predetermined time orstroke of the pulling apparatus and in this way can supply informationabout any rivets not set optimally.

It is preferable for a plurality of measured values to be obtained atregular time intervals during the application of the tensile force.Therefore, a time profile of the tensile force expended can bedetermined and in this way detailed information about the rivetedconnections can be obtained.

The use of measured data obtained with a piezoelectric pressure sensoris particularly advantageous. Under the high tensile forces which occur,even extremely small sensors supply sufficiently high voltages formeasurements which are precise and not susceptible to interference.

Finally, the invention relates to a head piece for a setting tool, whichcomprises a device comprising at least one piezoelectric sensor formeasuring the tension exerted by the pulling apparatus. In terms of itsfunction, this head piece corresponds to the achievement of the objectaccording to the invention as claimed in claim 60, with the differencethat, here, the device required for measuring the tension, together witha piezoelectric sensor, is integrated completely into the head piece. Inthis way it is possible to provide a head piece with the functionaccording to the invention for an existing setting implement. This hasthe advantage that no complete setting implement has to be bought. Thehead piece can be provided with appropriate connections for settingtools from different manufacturers. In this case, it is to the advantageof the head piece according to the invention that the piezoelectricsensor does not need any power supply.

Finally, the invention relates to a rivet. The setting implementaccording to the invention according to the features of claim 1 dependson uniformity of the setting operations when comparing measured values,such as the tension at a specific time in the setting operation. In thiscase, it is above all rivets which have different characteristics whichare disadvantageous. If the characteristics are very different, forexample because of different materials or because of fabricationtolerances, the implement cannot be programmed optimally. It is thennecessary for the tolerance limit for a setting operation to beincreased as well, which is in turn disadvantageous for an optimalsetting result. It was therefore also an object of the invention toprovide a rivet which has substantially constant characteristics.

This object is achieved in a surprisingly simple way by a method formonitoring a rivet as claimed in claim 97. According to said claim, atension is applied to the rivet, in particular using the setting tool asclaimed in claim 1 to 60, the change in length of the rivet is measuredand is compared with a desired value. In order not to damage the rivet,the measurement is performed in the elastic range. By using a desiredvalue of the length change or a distance/force curve, it is possible totest whether the rivet has the intended characteristics.

In a preferred development of the invention, the tension is applied tothe rivet pin of a blind rivet.

In a development of the invention, rivets which do not lie within apredefined tolerance band are separated out. The separation can becarried out automatically by the monitoring apparatus.

In a development of the invention, rivets which lie within a predefinedtolerance band are marked permanently. Thus, the quality check carriedout is visible on the rivet. Confusion with untested rivets is ruled outin this way.

The invention is to be explained in more detail below using preferredexemplary embodiments and with reference to the appended drawings,identical designations in the individual drawings referring to identicalor similar components.

FIG. 1 shows a schematic view of a first embodiment of the invention,

FIG. 2 shows graphs of the tension as a function of time, FIGS. 3A to 3Dshow various embodiments of external devices for the registration andevaluation of tension measured values,

FIG. 4 shows a schematic cross-sectional view through one embodiment ofthe invention,

FIG. 5 shows a schematic view of a head piece of a setting implementhaving sensors, and

FIG. 6 shows graphs of the tension of various set items as a function oftime.

In the following description, reference will primarily be made to therivet setting operation; this means the setting of a rivet. In thiscase, however, the rivet setting described comprises the setting ofblind rivets, riveted nuts and, in particular, also the setting oflocking ring bolts, even if this is no longer expressly mentioned. Tothe extent that a different head piece, mouthpiece, chuck or anotherholder is needed for the respective embodiment, those skilled in the artin this field can make appropriate adaptations to the currentrequirements.

FIG. 1 shows a schematic view of a first embodiment of the rivet settingimplement according to the invention. The rivet setting implement 1comprises a head piece 2 with adjusting nut 22 for holding a rivet 20, abody part 6 and a handle 16. Using a manually actuated triggering device18, a pulling apparatus in the interior of the rivet setting implementis triggered, being connected to a device for gripping the shank or thepin of the rivet 20, so that the pin is pulled into the implement. Inthis case, the device for gripping the shank or rivet pin preferablycomprises a chuck having two or more clamping jaws. The pullingapparatus is supported on the head part 2 of the rivet settingimplement, so that the tension exerted on the rivet pin is transformedinto a pressure exerted between head part and pulling apparatus. On thehead part 2 there is a sensor unit 3, preferably with piezoelectricsensor, which measures the pressure arising between head part 2 andpulling apparatus as the rivet pin is pulled. The sensor generates avoltage signal substantially proportional to the tension. This voltageis either transmitted directly via a cable 8 to an external device 12for registering and evaluating tension measured values or is initiallyamplified by the sensor unit, the amplified signal then beingtransmitted.

In addition, dedicated evaluation electronics 15 which, for example,comprise counting electronics with a date and/or time of day function,can be accommodated on a part 14 fixed to the handle.

As an alternative to a transmission via cable connections, thetransmission to an external evaluation unit can also be carried out byappropriate devices for the transmission and reception of infrared,ultrasound or radio signals. In particular, the rivet setting implementcan also be set up to transmit the signals via a mobile radio network toa terminal, by which means large distances between rivet settingimplement and external evaluation unit can be attained.

In this embodiment, the rivet setting implement 1 also further has adisplacement transducer 4, which determines the instantaneous positionof the pulling apparatus via a device for measuring the position of thepulling apparatus, and sends a corresponding signal to the externaldevice 12 via a cable connection 10. The displacement transducer can be,for example, an optoelectronic or else an inductive displacementtransducer.

FIG. 2 shows graphs of the tension as a function of time in the courseof rivet setting cycles. Here, graph 100 shows the typical curve of thetension under optimum conditions. The curve exhibits a minimum of thetension. As far as this minimum, the rivet head is compressed by thetensile force exerted by the pulling apparatus of the rivet settingimplement. After that, the tensile force increases again until the rivetpin shears off and the tension falls abruptly to zero.

Graphs 101, 102 and 103 show curves of the tension under non-optimalconditions. Here, graph 101 shows the curve of the tension in the caseof an excessively large hole diameter. In this case, the minimum betweenthe two maxima is not as low as in the optimum case and has a somewhatlater time. Up to the point where the pin shears off, in the case of anexcessively large hole diameter, a higher tension additionally has to beapplied and the pin shears off at a somewhat later time.

Graph 102 shows the curve of the tension in the case of a rivet notinserted completely into a hole, and graph 103 in the case of a rivetingoperation without material, that is to say without a rivet having beenplugged into a hole in a metal sheet. In both cases, the minimum of thetension and the time at which the pin shears off are located at a latertime as compared with the course of the curve under optimum conditions.

By using these graphs, it becomes clear that the curve of the tensionover time can give detailed information about the state of the setrivet.

In the following text, reference will be made to FIGS. 3A to 3D, whichshow embodiments of external devices for registering and evaluatingtension measured values of the invention.

In FIG. 3A, an evaluation unit 24 which is connected via a cableconnection 8 to the sensor unit 3 of the rivet setting implement 1 isshown schematically. Instead of the cable connection 8, the sensor unitand the evaluation unit could also be connected to each other via atransmitting/receiving device for infrared, ultrasound or radio signals,the sensor being equipped appropriately with a transmitter and/orreceiver.

The evaluation unit 24 comprises an LCD display 26 and operatingelements 28. Current results of measurements are shown on the LCDdisplay, such as the maximum tension reached. The measured and evaluatedresults are determined by suitable measurement electronics in the unit24. Via the operating elements, various functions, such as performing areference measurement, threshold values for warning messages orresetting the current measured values, can be entered.

FIG. 3B shows an expansion of this system, a printer 32 being connectedto the evaluation unit 24 via a cable connection 30. Via the printer 32,current measuring results and further data can be output. The printercan be driven, for example, via the operating elements 28.

FIG. 3C shows an embodiment in which the measured values from the sensorunit 3 of the rivet setting implement are transmitted via a cableconnection 8 to a computer 34 as evaluation unit. For this purpose, thecomputer, preferably a workstation computer, can be provided with asuitable plug-in board in which the evaluation electronics for thevoltage measured values transmitted are accommodated. For instance, thevoltage measured values are digitized at regular time intervals by meansof an ADC module and can then be further processed via suitablesoftware. The conditioned measured data and evaluation results are thendisplayed on the monitor 36 of the computer.

FIG. 3D shows a further embodiment, in which a plurality of rivetsetting implements is connected to an evaluation unit 38 via cableconnections 81, 82, 83 and 84. The embodiment is shown by way of examplein FIG. 3D for four rivet setting implements. However, this structurecan be expanded to as many implements as desired. The structure can alsolikewise be used for an individual rivet setting implement. Each rivetsetting implement is connected via the cable connections to one of theblocks 381 to 384 of the evaluation unit 38.

The evaluation unit 38 is in turn connected via a connection 40 to anetwork node 42, from which the data can be distributed to a pluralityof computers 341 to 344.

FIG. 4 shows a schematic cross-sectional view through an embodiment ofthe invention, by using which the principle of the tension measurementcan be explained. In the body part 6 there is a hydraulic cylinder 50.In the cylinder 60 there runs a hydraulic piston 52, to which a drawspindle 54 is fixed which transmits the force exerted by the piston to achuck 56 fixed thereto. If a force is exerted by the piston in thedirection of the arrow, by a suitable hydraulic fluid being forced intothe cylinder section 51, clamping jaws 58 are initially compressed bythe chuck 58 moving rearward until a rivet pin located between them isgripped and clamped in. The clamping jaws then pull the rivet pinfurther into the head part 2 of the rivet setting implement until itshears off the rivet head resting on the adjusting nut 22. The pistoncan also be operated hydropneumatically, the hydraulic fluid beingforced into the hydraulic cylinder 50 by a further, pneumaticallyoperated piston which, for example, can be accommodated in the part 14shown in FIG. 1 and fixed to the handle.

As a result of the tensile force exerted via the chuck 56, a pressure isexerted on the head part 2. The head part 2 is fixed to the body part 6in such a way that the pressure is not transmitted directly to thesleeve of the head part 2 but via a piezoelectric material part 31located between head part and body part. A piezoelectric voltageproduced as a result can then be transmitted by means of the electricalconnections 60 and 62 to a suitable connecting plug 64. Likewise, thepressure sensor can also be connected to suitable measuring andevaluation electronics, which are integrated in the rivet settingimplement itself.

FIG. 5 shows a schematic plan view of a head piece for a setting toolaccording to the invention. It is possible to see the adjusting nut 22of the head piece 2. Three sensors 70 are fitted around the adjustingnut 22. When the implement is placed, all three sensors make contactwith the part to be fixed only if the implement is at the correct anglewith respect to the part to be fixed. In this way, it is possible tomonitor whether the operator is making an error. If the implement is notplaced at the correct angle, an electronics unit ensures that theimplement is blocked, and the setting operation therefore cannot bestarted at all.

FIG. 6 shows four graphs, in which the tension exerted during a settingoperation is plotted against the time, the x-axis indicating the timeand the y-axis indicating the force. Graph 90 shows the force-time curvewhen setting a rivet nut. Here, the force initially rises sharply in theelastic region, changes into the plastic region and remainsapproximately constant as far as the end of the setting operation.Graphs 91, 92 and 93 show the force-time curve for various blind rivets.Here, the force also rises in the region of plastic deformation, untilthe rivet pin shears off and the force falls to zero. It can be seenthat the force-time curves for different rivets are very different. Itis therefore necessary to program the implement for specific settingoperations. By using deviations from these curves, a series of causes offaults can already be detected. For instance, in the case of a blindrivet, if the force rises later in the elastic region, the blind rivethas gripped only the part to be set. If the hole is too wide, the curverises less steeply in the plastic region. In this way, by means of acomparison with stored causes of faults, a whole series of faults can bedetected. It is likewise conceivable to measure a force-distance curveor even a force-time and a force-distance curve. By means of evaluatingsetting operations carried out, ideal values and typical deviations inthe case of specific causes of faults can be determined accurately. Theevaluation can be carried out by setting various reference fields 94,95, 96. If the curve runs past the field 94 on the right, then the blindrivet is gripping only the part to be fixed; if the change from theelastic into the plastic region does not take place exactly in field 95,then the drilled hole is too wide or, if the tension does not fall tozero in field 96, a wrong rivet has been used. Accurate fault analysisis carried out by means of many such fields, which are traversed duringthe setting operation and make it possible to detect a cause of a fault.By means of lining up individual fields, if the desired values arecomplied with, specific causes of faults are also ruled out. If, forexample, field 94 is complied with, the fact that the counterpart hasnot been gripped is ruled out. In this way, unambiguous allocation ofthe various causes of faults is possible.

1-101. (canceled)
 102. A rivet placing tool comprising: a head piece foradmission of a rivet; a mechanism for seizing and/or pulling a rivetingbolt; hauling equipment connected to said mechanism for seizing and/orpulling; means for measuring values occurring with the rivet placingtool; a mechanism for comparing said measured values with stored values;and a mechanism for the determination of a cause a deviation of saidmeasured values from said stored values from a quantity of storedcauses.
 103. A rivet placing tool comprising: a head piece for receivinga rivet; a device for gripping a riveting bolt; a pulling deviceconnected to the device for gripping, said pulling device forcontrolling riveted joints; and a device for measuring tensile stress onthe pulling device, said device for measuring allowing detection of afault by comparing measured variables of said tensile stress with storedvariables of said tensile stress.
 104. A setting tool comprising a headpiece for holding a rivet; a gripping device for gripping and/or pullingthe rivet; a pulling apparatus connected to the gripping device so thatthe rivet can be set in a surface; a measuring device for measuring ameasured value from said pulling apparatus; and a processor forcomparing said measured value with a stored value, said processordetermining a cause of a deviation of said measured value from saidstored value from a set of stored causes.
 105. The setting tool as inclaim 104, wherein said measured value comprises a value selected fromthe group consisting of a tension exerted by said pulling apparatus, aposition of said pulling apparatus, an elapsed time, an angle of thesetting tool to the surface, and any combinations thereof.
 106. Thesetting tool as in claim 104, wherein said set of stored causescomprises a cause selected from the group consisting of a implement notplaced at the correct angle fault, an incorrect rivet used fault, arivet damaged fault, a too wide hole fault, a too narrow hole fault, ano rivet fault, a rivet not gripping both parts to be connected fault, asetting tool defect fault, and any combinations thereof.
 107. Thesetting tool as in claim 104, wherein said measuring device comprises astrain gage or a piezoelectric sensor.
 108. The setting tool as in claim104, wherein said measuring device is capacitive sensor and saidmeasured value is a position of said pulling apparatus.
 109. The settingtool as in claim 104, wherein said measuring device comprises at leastthree sensors arranged on said head piece and said measured value is anangle of the setting tool to the surface.
 110. The setting tool as inclaim 104, further comprising a data storage device.
 111. The settingtool as in claim 110, wherein said data storage device is resettable.112. The setting tool as in claim 110, further comprising an independentpower source for said data storage device.
 113. The setting tool as inclaim 104, further comprising an independent power source for saidprocessor.
 114. The setting tool as in claim 104, further comprising acounter, said counter counting a variable selected from the groupconsisting of a number of rivet setting cycles, a number of faults, anumber of fault causes, and any combinations thereof.
 115. The settingtool as in claim 104, further comprising a registering device, saidregistering device registering a variable selected from the groupconsisting of a date, a time of day, and any combinations thereof. 116.The setting tool as in claim 104, further comprising an external unitand a transmitting device for transmitting said measured value from saidprocessor to said external unit.
 117. The setting tool as in claim 116,wherein said transmitting device comprises a device selected from thegroup consisting of an infrared transmitter, an ultrasound transmitter,a radio signal transmitter, and an optical conductor.
 118. The settingtool as in claim 116, wherein said external unit comprises a computingunit.
 119. The setting tool as in claim 116, wherein said external unitcomprises a mobile radio terminal.
 120. The setting tool as in claim104, wherein said processor is adapted to switch off the setting tool inresponse to said cause.
 121. The setting tool as in claim 104, whereinsaid processor is connectable to a local network.
 122. The setting toolas in claims 104, wherein said pulling apparatus comprises a drawspindle and said gripping device comprises a set of clamping jaws forclamping the rivet.
 123. The setting tool as in claim 104, wherein saidpulling apparatus is operated by a driving device selected from thegroup consisting of an electrical drive, a hydraulic drive, a pneumaticdrive, and any combinations thereof.
 124. The setting tool as in claim104, further comprising a test cycle for testing the setting tool. 125.A method for monitoring a rivet setting operation, comprising: insertinga rivet into a setting implement having a pulling apparatus; applying atensile force to said rivet via said pulling apparatus; measuring avariable associated with the rivet setting operation; comparing saidmeasured value to a stored value; and determining a cause for adeviations of said measured value from said stored value from a set ofstored causes.
 126. The method as in claim 125, wherein said measuredvalue comprises a value selected from the group consisting of saidtensile force, a position of said pulling apparatus, an elapsed time ofthe setting operation, an angle of said setting implement with respectto a surface on which said setting implement is placed, and anycombinations thereof.
 127. The method as in claim 125, wherein said setof stored causes comprises a cause selected from the group consisting ofa implement not placed at the correct angle fault, an incorrect rivetused fault, a rivet damaged fault, a too wide hole fault, a too narrowhole fault, a no rivet fault, a rivet not gripping both parts to beconnected fault, a setting tool defect fault, and any combinationsthereof.
 128. The method as in claim 125, further comprising counting avariable selected from the group consisting of a number of rivet settingcycles, a number of said deviations, a number of said causes, and anycombinations thereof.
 129. The method as in claim 125, furthercomprising registering a variable selected from the group consisting ofa date, a time of day, and any combinations thereof.
 130. The method asin claim 125, further comprising communicating a signal to an externalunit, said signal being selected from the group consisting of saidmeasured value, said cause, said deviation, and any combination thereof.131. The method as in claim 125, further comprising indicating saidcause to an operator.
 132. The method as in claim 125, furthercomprising turning off said setting implement in response to saiddeviation.
 133. A head piece for a setting tool, comprising: a measuringdevice for measuring a value occurring during a setting operation; acomparing device for comparing said values to a stored value; adetermining device for determining a cause of a deviation of said valuefrom said stored value from a set of stored causes.
 134. The head pieceas in claim 133, wherein said measured value comprises a value selectedfrom the group consisting of an elapsed time, an angle of the head pieceto a surface, and any combinations thereof.
 135. The head piece as inclaim 133, wherein said measuring device is a strain gage or apiezoelectric sensor for measuring tension.
 136. The head piece as inclaim 133, wherein said measuring device is a capacitive sensor formeasuring a pulling apparatus position.
 137. The head piece in claims133, wherein said measuring device is at least three sensors formeasuring an angle of the head piece.
 138. The head piece as in claims133, further comprising a data storage device.
 139. The head piece as inclaims 138, wherein said data storage device is resetable.
 140. The headpiece as in claims 133, further comprising an independent power sourcefor powering said comparing device and/or said determining device. 141.The head piece as in claim 133, further comprising a counter forcounting a variable selected from the group consisting of a number ofrivet setting cycles, a number of said deviations, a number of saidcauses, and any combinations thereof.
 142. The head piece as in claim133, further comprising a registering device for registering a variableselected from the group consisting of a date, a time of day, and anycombinations thereof.
 143. The head piece as in claim 133, furthercomprising a transmitting device for transmitting said measured value toan external unit.
 144. The head piece as in claim 133, furthercomprising a switching device for switching off the head piece inresponse to said deviation.
 145. The head piece as in claim 133, furthercomprising a connection device for connecting to a local network.
 146. Arivet setting tool comprising: a head piece for holding a rivet having arivet pin; a gripping device for gripping said rivet pin; a pullingapparatus connected to said gripping device; and at least onepiezoelectric sensor for measuring a tension exerted by said pullingapparatus on said rivet pin.
 147. The rivet setting tool as in claim146, further comprising a measuring device for measuring a position ofsaid pulling apparatus.
 148. The rivet setting tool as in claim 146,further comprising a pressure sensor for measuring said tension. 149.The rivet setting tool as in claim 148, wherein said pressure sensor isa piezoelectric pressure sensor.
 150. The rivet setting tool as in claim146, wherein said pulling apparatus comprises a drive selected from thegroup consisting of an electric drive, a hydraulic drive, a pneumaticdrive, and any combinations thereof.
 151. The rivet setting tool as inclaim 146, further comprising a communication device for communicatingsaid tension to an external unit.
 152. The rivet setting tool as inclaim 146, wherein said communicating device communicated said tensionto said external unit via a signal selected from the group consisting ofan infrared signal, an ultrasound signal, a radio signals, an opticalsignal, and any combinations thereof.
 153. The rivet setting tool as inclaim 146, further comprising a switching device for switching off therivet setting tool in response to said tension.
 154. A method formonitoring a rivet setting operation, comprising: gripping a rivet;applying a tensile force to said rivet; and obtaining at least onemeasured value during the application of said tensile force, said atleast one measured value being caused or influenced by said tensileforce.
 155. The method as in claim 154, wherein said at least onemeasured value comprises a plurality of measured values obtained atregular time intervals during the application of said tensile force.156. The method as in claims 154, further comprising comparing saidleast one measured value to a desired value.
 157. The method as in claim156, further comprising outputting a fault message if said at least onemeasured value deviates from said desired value.
 158. A method formonitoring a rivet during a setting operation, comprising: applying atension the rivet; measuring a change in length of the rivet; andcomparing said change in length to a desired value.
 159. The method asin claim 158, further comprising separating out the rivet if said changeis outside a predefined tolerance band from said desired value.
 160. Themethod as in claim 158, further comprising marking the rivet if saidchange is within a predefined tolerance band from said desired value.